How do you calculate a pitcher's ERA?
I know it stands for earned run average and the lower the better. What I don't understand is how it's calculated, what potential range there is (can someone have an ERA of zero? Could it go really high?) What does it mean? If a pitcher leaves men on base when he gets taken out and they score on the next pitcher, does that affect his ERA? What if they get stranded? What's a good ERA? What's a bad one? What's a really high ERA? Have pitchers always had them/used them to distinguish the quality of pitchers?
Comments
OK, get out a pen and paper:
ERA for the season is calculated by putting the amount of earned runs a pitcher has allowed over the amount of innings he has pitched, and then cross multiplying that by x/9. The variable "x" will be his ERA.
So let's say pitcher John Hamilton has pitched 46 innings so far this year, and he has given up a total of 8 earned runs. Put 8 over 46 (8/46), and cross multiply that with x/9. 8 times 9 is 72, and 46 times x is 46x. So what we're left with is 46x = 72. Divide 72 by 46, and the (rounded up) answer is 1.57.
Remember, too, that when you're inputting the amount of innings that a pitcher has pitched, if he has pitched 21 and two-thirds innings, he has pitched 21 2/3, NOT 21.2.
As for your other questions, a pitcher can have an ERA of 0.00 if he has not allowed any runs for the season (assuming that you're looking at his season statistics; if you want to know his career ERA, he'll have had to have surrendered 0 earned runs for his career.) If a pitcher leaves the game with runners on second and third, and the relief pitcher lets them both in, both of those runs are charged to the original pitcher; however, in that scenario, once both of the runners who were on base when score, the original pitcher's day is done. That is to say, he won't be responsible for the runner who is on base that the relief pitcher allowed to reach base.
If a pitcher leaves the game with runners on second and third base and they end up stranded, then his ERA is unaffected.
A "good" ERA is subjective. In this era of baseball, a good ERA is usually lower than 4. Lower than 3 is very good, lower than 2 is outstanding, and lower than 1 is almost unheard of.
1. Earned Runs x 9 / Innings Pitched
2. Range 0 - Infinity, if someone comes in and pitches 0 innings, ie doesn't get anyone out, you can't calculate an ERA but if a pitcher comes in and gets one out and gives up 5 runs, his ERA would be 135.00.
3. If a pitcher leaves men on, he does get charged with the runs if they score. If they're stranded it doesn't do anything.
4. I would consider a good ERA to be below 4.00 and if it's above that it starts to get into bad territory. Really high is usually 7.00+
5. ERA has been around for about a century as a general measure of how responsible a pitcher is if the team is giving up a lot of runs or little. Now, with the sabermetric revolution, there are a lot of different metrics used to evaluate pitchers.
ERA is used to determine the average number of runs a pitcher will give up in a complete game. Because different levels play different number of innings the normal number of innings in a game needs to be part of the formula.
ERA is calculated by (EARNED RUNS * NUMBER OF INNINGS IN A NORMAL GAME) / INNINGS PITCHED
So if a pitcher gave up 5 runs in 12.33 innings his ERA would be...
Majors: (5 * 9) / 12.33 = 3.65 ERA
High School: (5 * 7) / 12.33 = 2.84 ERA
Little League: (5 * 6) / 12.33 = 2.43 ERA
An ERA of 0.00 is possible. Trevor Hoffman has pitched 16.0 innings this year without giving up a run so his ERA is (0 * 9) / 16 = 0.00
If a pitcher gives up at least one run and fails to get anybody out then their ERA will be defined as infinity.
Any runners left on base when a pitcher leaves the game are his responsibility. If they end up scoring off the next pitcher they may or may not affect the previous pitcher's ERA. It depends on how they got on base and how they scored. They could be considered Unearned Runs which does not affect ERA.
A good ERA in the majors nowadays is under 4:00. Really good pitchers will have an ERA under 3.00.
To calculate a pitcher's earn run average:
ERA = (earned runs X 9) / number of innings pitched
ERA = (earned runs*9)/innings pitched. 56 K's is awesome, 12 earned runs is a 3.00 ERA
ERA=Games Pitched/Earned Runs
Depending on what level you are at, the definition of a game pitched varies. In Little league, it is 6 innings. Thus, if a pitcher throws 12 innings, he has 2 games. 15 innings, he has 2.5 games.
(EArned runs in a game) x (Number of innings pitched) and take that number and divide it by 9